NASCLA Accredited Commercial General ContractorMasonryMedium
A masonry project involves constructing a long, uninterrupted brick wall (over 25 feet). To accommodate thermal expansion and contraction and prevent uncontrolled cracking, which of the following is the most appropriate design consideration?
- ASpecify a higher compressive strength mortar, such as Type M.
- BIncorporate properly designed and spaced expansion joints.
- CIncrease the amount of horizontal joint reinforcement throughout the wall.
- DInstall larger, deeper weep holes at regular intervals along the base.
Show answer & explanationAnswer & explanation
Correct answer: B. Incorporate properly designed and spaced expansion joints.
Expansion joints are specifically designed to absorb movement caused by thermal expansion and contraction, as well as moisture expansion, in long masonry walls. Without them, these movements can lead to uncontrolled cracking.
Why the other options are wrong
- A. Mortar strength primarily relates to load-bearing capacity, not directly to accommodating large-scale thermal movement.
- C. While horizontal reinforcement helps control shrinkage cracking, it is not designed to accommodate significant thermal expansion over long lengths without expansion joints.
- D. Weep holes are for moisture drainage and do not address thermal movement.
Expansion Joints in Masonry
Vertical, continuous, unobstructed gaps filled with a compressible material, designed to permit volumetric changes (expansion and contraction) in masonry walls.
- Accommodates thermal and moisture movement.
- Prevents uncontrolled cracking.
- Typically placed at corners, changes in wall height/thickness, and long runs.
- Filled with flexible sealant and backer rod.
Memory trick: Long walls need 'space' to breathe and grow.